1. Field of the Invention
The present invention relates to a method for artificially allocating (arranging or orienting) cells, at a specific zone on the surface of a substrate, which express their functions by such allocating, for example, cells in the nervous system, liver, kidney, etc., thereby to reconstruct an in vivo order outside the living body, i.e., in vitro, and a device therefor. The present invention also relates to a method for inputting and outputting in vitro the functions expressed by the cells allocated by the method for allocating and then cultured and an apparatus therefor.
2. Description of the Related Art
In recent years, it has been made possible to culture cells in the nervous system, liver, kidney, etc. in a dissociated state in vitro, due to the progress of cell culture techniques. However, these cells express their function in their order. For example, neurons are connected with each other in vital tissues to form circuits, whereby the function of information processing is expressed. Accordingly, if .these cells are allocated and cultured in vitro, it would be possible to artificially prepare biological devices having various functions.
In order to make the cells in these tissues dissociate in vitro for incubation of these cells, however, the cell order possessed in the tissues is destroyed. As the result, a problem occurs that their functions are lost, although it is possible to culture the cells.
On the other hand, it is possible to culture cells without disconnecting the cells as they are in the tissues withdrawn from the living body. However, the respective cells in the tissues cannot be identified. After all, it has been difficult to express the function desired to be utilized. For example, while it has been wished to utilize input and output signals at a specific neural circuit in the nerve tissue, the neurons for constructing the neural circuit could not be specified so that it has been impossible to utilize the desired input and output signals.
As one method for allocating specific cells once dissociated on the surface of the same culture substrate and reconstructing the allocating in order to eliminate problems, a machine for sorting cells one by one comprising a combination of a cell sorter and an apparatus for stepping operation of a culture dish has been provided for practical use. However, the machine requires as many repetitions of the sorting operation as the number of the cells to be sorted. In addition, when one cell was plated on the surface of the culture substrate, the next cell would then be put on the surface of the culture substrate so that it was difficult to arrange many cells rapidly in a simple manner.
Another method comprises providing a multicompartment chamber on a culture substrate having narrow grooves on its surface, introducing a suspension of neurons via one chamber, precipitating and adhering the cells onto the culture substrate at a specific position, and culturing the culture substrate to perform elongation of neurites via the groove (Proc. Natl. Acad. Sci. USA, Vol. 74, No. 10, pp. 4516-4519, 1977 and Science, Vol. 244, pp. 585-587, 1989). According to this method, however, there is a danger that the multicompartment chamber might inhibit physically and biologically the elongation of neurites and expression of the functions. The method involves an additional drawback that interaction of the cells cannot be observed upon incubation so that the relationship between cells connected with each other cannot be specified.
Furthermore, in order to reconstruct the order of cells in vivo and utilize their functions, the system should be kept sterile and needless to say, the cells should not be damaged. Simple operation makes maintenance of sterility easy and rapid processing results in no damage of the cell activity during the processing. From a practical viewpoint, these are important factors which should not be underrated.